// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/base/bit_reader.h"

#include <stddef.h>
#include <stdint.h>

#include "base/macros.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace media {

static void SetBit(uint8_t* buf, size_t size, size_t bit_pos)
{
    size_t byte_pos = bit_pos / 8;
    bit_pos -= byte_pos * 8;
    DCHECK_LT(byte_pos, size);
    buf[byte_pos] |= (1 << (7 - bit_pos));
}

TEST(BitReaderTest, NormalOperationTest)
{
    uint8_t value8;
    uint64_t value64;
    // 0101 0101 1001 1001 repeats 4 times
    uint8_t buffer[] = { 0x55, 0x99, 0x55, 0x99, 0x55, 0x99, 0x55, 0x99 };
    BitReader reader1(buffer, 6); // Initialize with 6 bytes only

    EXPECT_TRUE(reader1.ReadBits(1, &value8));
    EXPECT_EQ(value8, 0);
    EXPECT_TRUE(reader1.ReadBits(8, &value8));
    EXPECT_EQ(value8, 0xab); // 1010 1011
    EXPECT_TRUE(reader1.ReadBits(7, &value64));
    EXPECT_TRUE(reader1.ReadBits(32, &value64));
    EXPECT_EQ(value64, 0x55995599u);
    EXPECT_FALSE(reader1.ReadBits(1, &value8));
    value8 = 0xff;
    EXPECT_TRUE(reader1.ReadBits(0, &value8));
    EXPECT_EQ(value8, 0);

    BitReader reader2(buffer, 8);
    EXPECT_TRUE(reader2.ReadBits(64, &value64));
    EXPECT_EQ(value64, 0x5599559955995599ull);
    EXPECT_FALSE(reader2.ReadBits(1, &value8));
    EXPECT_TRUE(reader2.ReadBits(0, &value8));
}

TEST(BitReaderTest, ReadBeyondEndTest)
{
    uint8_t value8;
    uint8_t buffer[] = { 0x12 };
    BitReader reader1(buffer, sizeof(buffer));

    EXPECT_TRUE(reader1.ReadBits(4, &value8));
    EXPECT_FALSE(reader1.ReadBits(5, &value8));
    EXPECT_FALSE(reader1.ReadBits(1, &value8));
    EXPECT_TRUE(reader1.ReadBits(0, &value8));
}

TEST(BitReaderTest, SkipBitsTest)
{
    uint8_t value8;
    uint8_t buffer[] = { 0x0a, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
    BitReader reader1(buffer, sizeof(buffer));

    EXPECT_TRUE(reader1.SkipBits(2));
    EXPECT_TRUE(reader1.ReadBits(3, &value8));
    EXPECT_EQ(value8, 1);
    EXPECT_TRUE(reader1.SkipBits(11));
    EXPECT_TRUE(reader1.ReadBits(8, &value8));
    EXPECT_EQ(value8, 3);
    EXPECT_TRUE(reader1.SkipBits(76));
    EXPECT_TRUE(reader1.ReadBits(4, &value8));
    EXPECT_EQ(value8, 13);
    EXPECT_FALSE(reader1.SkipBits(100));
    EXPECT_TRUE(reader1.SkipBits(0));
    EXPECT_FALSE(reader1.SkipBits(1));
}

TEST(BitReaderTest, VariableSkipBitsTest)
{
    uint8_t buffer[256] = { 0 };

    // The test alternates between ReadBits and SkipBits.
    // The first number is the number of bits to read, the second one is the
    // number of bits to skip. The number of bits to read was arbitrarily chosen
    // while the number of bits to skip was chosen so as to cover from small skips
    // to large skips.
    const size_t pattern_read_skip[][2] = {
        { 5, 17 },
        { 4, 34 },
        { 0, 44 },
        { 3, 4 }, // Note: aligned read.
        { 7, 7 }, // Note: both read&skip cross byte boundary.
        { 17, 68 },
        { 7, 102 },
        { 9, 204 },
        { 3, 408 }
    };

    // Set bits to one only for the first and last bit of each read
    // in the pattern.
    size_t pos = 0;
    for (size_t k = 0; k < arraysize(pattern_read_skip); ++k) {
        const size_t read_bit_count = pattern_read_skip[k][0];
        if (read_bit_count > 0) {
            SetBit(buffer, sizeof(buffer), pos);
            SetBit(buffer, sizeof(buffer), pos + read_bit_count - 1);
            pos += read_bit_count;
        }
        pos += pattern_read_skip[k][1];
    }

    // Run the test.
    BitReader bit_reader(buffer, sizeof(buffer));
    EXPECT_EQ(bit_reader.bits_available(), static_cast<int>(sizeof(buffer) * 8));
    for (size_t k = 0; k < arraysize(pattern_read_skip); ++k) {
        const size_t read_bit_count = pattern_read_skip[k][0];
        if (read_bit_count > 0) {
            int value;
            EXPECT_TRUE(bit_reader.ReadBits(read_bit_count, &value));
            EXPECT_EQ(value, 1 | (1 << (read_bit_count - 1)));
        }
        EXPECT_TRUE(bit_reader.SkipBits(pattern_read_skip[k][1]));
    }
}

TEST(BitReaderTest, BitsReadTest)
{
    int value;
    bool flag;
    uint8_t buffer[] = { 0x0a, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
    BitReader reader1(buffer, sizeof(buffer));
    EXPECT_EQ(reader1.bits_available(), 120);

    EXPECT_TRUE(reader1.SkipBits(2));
    EXPECT_EQ(reader1.bits_read(), 2);
    EXPECT_EQ(reader1.bits_available(), 118);
    EXPECT_TRUE(reader1.ReadBits(3, &value));
    EXPECT_EQ(reader1.bits_read(), 5);
    EXPECT_EQ(reader1.bits_available(), 115);
    EXPECT_TRUE(reader1.ReadFlag(&flag));
    EXPECT_EQ(reader1.bits_read(), 6);
    EXPECT_EQ(reader1.bits_available(), 114);
    EXPECT_TRUE(reader1.SkipBits(76));
    EXPECT_EQ(reader1.bits_read(), 82);
    EXPECT_EQ(reader1.bits_available(), 38);
}

} // namespace media
